Go JSON

Go has built-in support for JSON encoding and decoding. it also supports custom datatypes.

The Marshal function is used to convert go data types into JSON format.

Marshal function syntax is:

Marshal returns the JSON encoding of v.

Boolean is converted to JSON booleans. Floating point, integer, and Number are converted to JSON numbers. The map's key type must either be a string, an integer type, or implement encoding.TextMarshaler.

The decoding of JSON is done using Unmarshal function.

Unmarshal function syntax is:

Unmarshal decodes JSON-encoded value and stores the result in the value pointed to by v. If v is nil or not a pointer, Unmarshal returns an InvalidUnmarshalError.

We can also customize the fields stored under the "json" key in the struct field's tag. we can have name of the field, followed by a comma-separated list of options. Like

Field int 'json:"myName"' // The appears in JSON as key "myName".
Field int 'json:"myName,omitempty?'// The field is omitted from the object if its value is empty,
Field int 'json:"-"' //// Field is ignored by this package.

Go JSON Example 1

package main
import "encoding/json"
import "fmt"

func main() {
	bolType, _ := json.Marshal(false) //boolean Value
	fmt.Println(string(bolType))
	intType, _ := json.Marshal(10) // integer value
	fmt.Println(string(intType))
	fltType, _ := json.Marshal(3.14) //float value
	fmt.Println(string(fltType))
	strType, _ := json.Marshal("JavaTpoint") // string value
	fmt.Println(string(strType))
	slcA := []string{"sun", "moon", "star"} //slice value
	slcB, _ := json.Marshal(slcA)
	fmt.Println(string(slcB))
	mapA := map[string]int{"sun": 1, "moon": 2} //map value
	mapB, _ := json.Marshal(mapA)
	fmt.Println(string(mapB))
}

Output:

false
10
3.14
"JavaTpoint"
["sun","moon","star"]
{"moon":2,"sun":1}

Go JSON Example 2 (User Defined Data Type)

package main

import (
	"encoding/json"
	"fmt"
	"os"
)

type Response1 struct {
	Position   int
	Planet []string
}
type Response2 struct {
	Position   int      'json:"position"'
	Planet []string 'json:"planet"'
}

func main()  {
	res1A := &Response1{
		Position:   1,
		Planet: []string{"mercury", "venus", "earth"}}
	res1B, _ := json.Marshal(res1A)
	fmt.Println(string(res1B))

	res2D := &Response2{
		Position:   1,
		Planet: []string{"mercury", "venus", "earth"}}
	res2B, _ := json.Marshal(res2D)
	fmt.Println(string(res2B))


	byt := []byte('{"pi":6.13,"place":["New York","New Delhi"]}`)
	var dat map[string]interface{}
	if err := json.Unmarshal(byt, &dat); err != nil {
		panic(err)
	}
	fmt.Println(dat)
	num := dat["pi"].(float64)
	fmt.Println(num)
	strs := dat["place"].([]interface{})
	str1 := strs[0].(string)
	fmt.Println(str1)
	
	
	str := `{"Position": 1, "Planet": ["mercury", "venus"]}`
	res := Response2{}
	json.Unmarshal([]byte(str), &res)
	fmt.Println(res)
	fmt.Println(res.Planet[1])
	enc := json.NewEncoder(os.Stdout)
	d := map[string]string{"1":"mercury" , "2": "venus"}
	enc.Encode(d)

}

Output:

{"Position":1,"Planet":["mercury","venus","earth"]}
{"position":1,"planet":["mercury","venus","earth"]}
map[pi:6.13 place:[New York New Delhi]]
6.13
New York
{1 [mercury venus]}
venus
{"1":"mercury","2":"venus"}

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